The semi-circular square is divided into nine pieces like a cake. They can be seen clearly from the air. The nine pieces refer to the nine wealthy merchants who came to power and ruled the Tuscan city in the 13th century. The square is famous for the "Palio", a horse race which dates back to the 15th century. It features 17 riders on horses without saddles who represent the different of the city. Theo participants ride around the square three times. It takes place ever year on 2 July and 16 August and is seen as one of the toughest horse races worldwide.